Shoelace-Tying Robot With Only Two Motors

Many things that humans do are very difficult for machines. Case in point: tying shoelaces. Think of the intricate dance of fingers crossing over fingers that it takes to pass off a lace from one hand to the other. So when a team of five students from UC Davis got together and built a machine that got the job done with two hooks, some very clever gears, and two motors, we have to say that we’re impressed. Watch it in action on Youtube (also embedded below).

The two-motor constraint would seem at first to be a show-stopper, but now that we’ve watched the video about a hundred times, we’re pretty convinced that a sufficiently clever mechanical engineer could do virtually anything with two motors and enough gears. You see, the secret is that one motor is dedicated to moving a drive gear back and forth to multiple destinations, and the other motor provides the power.

This being Hackaday, I’m sure that some of you are saying “I could do that with one motor!” Consider that a challenge.

At first while watching I was like: “Ha, it can’t even tighten the first simple knot, this machine will not do a good job!”, 5 secons later, i’m here, speechless, with many questions that need answering.

Theoretically, you could even use just one motor if one rotation direction selects the function sequence and the other direction executes it. In practice this would be ridiculously complex mechanism of course.

some of the newer lego technic sets have multi function gear boxes for this kind of thing. like a single motor controlling several functions. this just puts a second motor in control of the mode switching.

I have been sitting here watching this in slo mo, which is a real change as I normally watch tech stuff at 2X and I am still in awe of how the line between simplicity and complexity blurs. Very cool machine.

this is fun! Very interesting to see the gear shifting, You would say it would be easier cheaper better to do this with more motors. But this if perhaps far more interesting to watch, nice job! Thanks for posting.

Also looked at the automaton video as mentioned in this post. That was perhaps even more amazing. What I mostly wonder is how they made the cams to operate the automaton, in order to make such a wonderful picture. I must have took a very very long time to create the cams for all axis. I know it is essentially clockwork technology with a extra levers operated by carefully shaped cams. But see it operate is like magic. For one reason I want to learn all there is about it (how they made it what challenges they experienced with the tools of that time) and on the other side I want to preserve the magic (by staying away from all possible info). But anyway, it wouldn’t hurt if hackaday did a special item about automatons.

You don’t need to go that far back. the allis chalmers round baler used a fully automatic baling, twine knotting and cutting system without hydraulics or electrics. It was probably the peak of mechanical ingenuity for round balers to this day.

we’re pretty convinced that a sufficiently clever mechanical engineer could do virtually anything with two motors and enough gears. You see, the secret is that one motor is dedicated to moving a drive gear back and forth to multiple destinations, and the other motor provides the power.

This being Hackaday, I’m sure that some of you are saying “I could do that with one motor!” Consider that a challenge.

That kind of mechanism has been done for years in Lego, because the programmable bricks have a limited number of motor ports (and, even if you had more ports, additional motors are more expensive than the parts to build a mechanical multiplexer). And yes, there are single-motor versions. The limitation of those is that they can only advance through the outputs in one order, and they usually can only turn the outputs in one direction.

The important bit here is the simplification of the actual knot tying. Instead of finger twiddling, reduce it to making two loops and pass one through another. I tie my shoelaces like that too, it tends to confuse people a bit.

Me too. I first learned that that method existed from a Sprint “Sprintcuts” ad (where they showed quick ways to do everyday things to highlight how fast their network is), but the ad didn’t show enough detail for me to figure it out, so I found a pretty good video on YouTube that showed how to do it. Unfortunately, I’ve never been able to refind that video to thank the person. It was a video of low production quality (just somebody who doesn’t normally make videos, using whatever camera they had).